Semiconductor Device and Method

ABSTRACT

A through via comprising sidewalls having first scallops in a first region and second scallops in a second region and a method of forming the same are disclosed. In an embodiment, a semiconductor device includes a first substrate; and a through via extending through the substrate, the substrate including a first plurality of scallops adjacent the through via in a first region of the substrate and a second plurality of scallops adjacent the through via in a second region of the substrate, each of the scallops of the first plurality of scallops having a first depth, each of the scallops of the second plurality of scallops having a second depth, the first depth being greater than the second depth.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional of and claims the benefit of U.S. patent application Ser. No. 16/746,017, filed on Jan. 17, 2020, and entitled “Semiconductor Device and Method,” which application is incorporated herein by reference.

BACKGROUND

Semiconductor devices are used in a variety of electronic applications, such as, for example, personal computers, cell phones, digital cameras, and other electronic equipment. Semiconductor devices are typically fabricated by sequentially depositing insulating or dielectric layers, conductive layers, and semiconductor layers of material over a semiconductor substrate, and patterning the various material layers using lithography to form circuit components and elements thereon.

The semiconductor industry continues to improve the integration density of various electronic components (e.g., transistors, diodes, resistors, capacitors, etc.) by continual reductions in minimum feature size, which allow more components to be integrated into a given area. However, as the minimum features sizes are reduced, additional problems arise that should be addressed.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the following detailed description when read with the accompanying figures. It is noted that, in accordance with the standard practice in the industry, various features are not drawn to scale. In fact, the dimensions of the various features may be arbitrarily increased or reduced for clarity of discussion.

FIGS. 1, 2A, 2B, 3A, 3B, 4, 5, 6, 7, 8A, 8B, and 9 are cross-sectional views of intermediate stages in the manufacturing of a semiconductor device, in accordance with some embodiments.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, or examples, for implementing different features of the invention. Specific examples of components and arrangements are described below to simplify the present disclosure. These are, of course, merely examples and are not intended to be limiting. For example, the formation of a first feature over or on a second feature in the description that follows may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features may be formed between the first and second features, such that the first and second features may not be in direct contact. In addition, the present disclosure may repeat reference numerals and/or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed.

Further, spatially relative terms, such as “beneath,” “below,” “lower,” “above,” “upper” and the like, may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. The spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. The apparatus may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein may likewise be interpreted accordingly.

Various embodiments provide improved through vias and methods of forming the same for use in semiconductor devices. The through vias may be formed using a first patterning process followed by a second patterning process having different process conditions from the first patterning process. The first patterning process etches a first region of the through vias and forms first scallops in sidewalls of the through vias. The second patterning process etches a second region of the through vias and forms second scallops in sidewalls of the through vias having depths different from depths of the first scallops. A metal layer is then deposited in the through vias. By using different patterning processes, which produce different depths of scallops in the first region and the second region of the through vias, the conductivity of the metal layer can be controlled in the first region and the second region, without requiring additional deposition and etching steps. The metal layer and the through vias may be used to provide shielding in microelectromechanical systems (MEMS) devices, light emitting diode (LED) devices, electron beam devices (e.g., an electron-beam writer control device), or the like.

FIG. 1 illustrates a first semiconductor substrate 100 having a patterned photoresist 102 formed on a top surface thereof, in accordance with some embodiments. The first semiconductor substrate 100 may include a bulk semiconductor substrate, semiconductor-on-insulator (SOI) substrate, multi-layered semiconductor substrate, or the like. The semiconductor material of the first semiconductor substrate 100 may be silicon, germanium, a compound semiconductor including silicon germanium, silicon carbide, gallium arsenic, gallium phosphide, indium phosphide, indium arsenide, and/or indium antimonide; an alloy semiconductor including SiGe, GaAsP, AlInAs, AlGaAs, GaInAs, GaInP, and/or GaInAsP; or combinations thereof. Other substrates, such as multi-layered or gradient substrates, may also be used. The first semiconductor substrate 100 may be doped or undoped. Devices (not separately illustrated), such as transistors, capacitors, resistors, diodes, and the like, may be formed in and/or on an active surface (e.g., the surface facing upward) of the first semiconductor substrate 100.

The patterned photoresist 102 is formed over the top surface of the first semiconductor substrate 100. A layer of photoresist material may be deposited over the first semiconductor substrate 100 using spin coating or the like. The photoresist material may then be patterned by exposing the photoresist material to a patterned energy source (e.g. patterned light) and subsequently exposing the photoresist material to a developer to remove exposed or unexposed portions of the photoresist material, forming the patterned photoresist 102. The portions of the photoresist material removed by the developer may correspond to openings which are subsequently formed in the first semiconductor substrate 100 (e.g., first openings 104, discussed below with respect to FIGS. 2A and 2B).

FIGS. 2A and 2B illustrate a formation of first openings 104 in the first semiconductor substrate 100 using the patterned photoresist 102 as a mask, in accordance with some embodiments. FIG. 2B illustrates a detailed view of region 106 of FIG. 2A. A first patterning process may be used to etch a first region 104 a of the first openings 104 having first scallops 108 a in the sidewalls thereof. A second patterning process following the first patterning process may be used to etch a second region 104 b of the first openings 104 having second scallops 108 b in the sidewalls thereof. In various embodiments, the first patterning process and the second patterning process may be Bosch processes, other deep reactive ion etching (DRIE) processes, or the like. The first scallops 108 a and the second scallops 108 b may be used to control the conductivity of a first metal layer (e.g., first metal layer 110, discussed below with respect to FIGS. 3A and 3B) deposited over the first semiconductor substrate 100 and in the first openings 104.

The first patterning process used to form the first region 104 a of the first openings 104 includes first depositions and first etchings. Each of the first depositions is followed by one of the first etchings and this pattern is repeated for a number of iterations. The first depositions and the first etchings may both be plasma-based processes and, in some embodiments, may both use fluorine-based plasmas. The first depositions are used to deposit a passivation film over patterned photoresist 102 and over portions of the first semiconductor substrate 100 exposed by the patterned photoresist 102. The first etchings are then used to etch through portions of the passivation film at the bottom of openings in the patterned photoresist which expose the first semiconductor substrate 100 and to etch the first semiconductor substrate 100.

The first etchings may be largely isotropic, but may include some ions which attach in a nearly vertical direction. This causes the first etchings to penetrate through portions of the passivation film disposed at the bottom of the openings without penetrating through the sidewalls of the passivation film, which causes the first patterning process to pattern the first region 104 a of the first openings 104 with substantially vertical sidewalls. The isotropic nature of the first etchings causes the first scallops 108 a to be formed in sidewalls of the first openings 104 in the first region 104 a. The number of iterations of the first patterning process used to form the first region 104 a of the first openings 104 may be from 50 to 150 iterations, such as 84 iterations; however, any other number of iterations required to etch the first region 104 a of the first openings 104 to a desired depth may be used.

Each iteration of the first patterning process extends the first openings 104 into the first semiconductor substrate 100 and forms one of the first scallops 108 a around the circumference of the first openings 104. Each of the first scallops 108 a may have a depth S₁ from about 40 nm to about 50 nm, such as about 45 nm. The first patterning process may be repeated until the first region 104 a reaches a depth D₁ from about 4 μm to about 17 μm, such as about 10 μm.

The first depositions may be performed at a pressure from about 5 mTorr to about 200 mTorr, such as about 40 mTorr. The first depositions may be performed for a period from about 0.5 seconds to about 5 seconds, such as about 0.9 seconds. A plasma power in a range from about 1000 W to about 3000 W, such as about 2500 W, may be used for the first depositions.

The first depositions may utilize a primary deposition gas and a secondary deposition gas, which each include fluorine-containing gases such as difluoromethane (CH₂F₂), octafluoropropane (C₃F₈), octafluorocyclobutane (C₄F₈), sulfur hexafluoride (SF₆), combinations thereof, or the like. In some embodiments, a carrier gas, such as argon (Ar), may be included in the primary deposition gas and/or the secondary deposition gas. In an embodiment, the primary deposition gas includes octafluorocyclobutane at a flowrate from about 100 sccm to about 800 sccm, such as about 360 sccm and sulfur hexafluoride at a flowrate from about 0 sccm to about 100 sccm, such as about 1 sccm. The secondary deposition gas may include octafluorocyclobutane at a flowrate from about 10 sccm to about 500 sccm, such as about 150 sccm.

The first etchings are performed at a pressure from about 5 mTorr to about 200 mTorr, such as about 23 mTorr, for a period from about 0.5 seconds to about 5 seconds, such as about 1.5 seconds, with a primary plasma power in a range from about 1000 W to about 3000 W, such as about 2500 W and a secondary plasma power in a range from about 50 W to about 1000 W, such as about 400 W. The first etchings may be performed using a substrate bias which ramps from a first substrate bias during the first iteration of the first patterning process to a second substrate bias during the last iteration of the first patterning process. The first substrate bias may be from about 5 W to about 1000 W, such as about 150 W and the second substrate bias may be from about 5 W to about 1000 W, such as about 270 W.

The first etchings may utilize a primary etching gas and a secondary etching gas, which each include fluorine-containing gases such as difluoromethane (CH₂F₂), octafluoropropane (C₃F₈), octafluorocyclobutane (C₄F₈), sulfur hexafluoride (SF₆), combinations thereof, or the like. In some embodiments, a carrier gas, such as argon (Ar), may be included in the primary etching gas and/or the secondary etching gas. In an embodiment, the primary etching gas includes octafluorocyclobutane at a flowrate from about 5 sccm to about 100 sccm, such as about 30 sccm and sulfur hexafluoride at a flowrate from about 50 sccm to about 500 sccm, such as about 250 sccm. The secondary deposition gas may include octafluorocyclobutane at a flowrate from about 0 sccm to about 100 sccm, such as about 1 sccm and sulfur hexafluoride at a flowrate from about 0 sccm to about 500 sccm, such as about 100 sccm.

The second patterning process used to form the second region 104 b of the first openings 104 includes second depositions, second etchings, and third etchings. Each of the second depositions is followed by one of the second etchings, which is followed by one of the third etchings, and this pattern is repeated for a number of iterations. The second depositions, the second etchings, and the third etchings may be plasma-based processes and, in some embodiments, may use fluorine-based plasmas. The second depositions are used to deposit a passivation film over patterned photoresist 102 and over portions of the first semiconductor substrate 100 exposed in the first openings 104. The second etchings and the third etchings are then used to etch through portions of the passivation film at the bottom of the first openings 104 and to etch the first semiconductor substrate 100.

The second etchings and the third etchings may be largely isotropic, but may include some ions which attach in a nearly vertical direction. This causes the second etchings and the third etchings to penetrate through portions of the passivation film disposed at the bottom of the first openings 104 without penetrating through the sidewalls of the passivation film, which causes the second patterning process to pattern the second region 104 b of the first openings 104 with substantially vertical sidewalls. The isotropic nature of the second etchings and the third etchings causes the second scallops 108 b to be formed in sidewalls of the first openings 104 in the second region 104 b. The second etchings and the third etchings may each have similar process parameters and be performed for a similar time to the first etchings and therefore the combination of the second etchings and the third etchings may produce larger second scallops 108 b in the second region 104 b than the first scallops 108 a produced by the first etchings in the first region 104 a. Each iteration of the second patterning process may also proceed for a duration greater than each iteration of the first patterning process. The number of iterations of the second patterning process used to form the second region 104 b of the first openings 104 may be from 50 to 500 iterations, such as 105 iterations; however, any other number of iterations required to etch the second region 104 b of the first openings 104 to a desired depth may be used.

Each iteration of the second patterning process extends the first openings 104 into the first semiconductor substrate 100 and forms one of the second scallops 108 b around the circumference of the first openings 104. Each of the second scallops 108 b may have a depth S₂ from about 150 nm to about 180 nm, such as about 165 nm. In various embodiments, a ratio of the depth S₁ to the depth S₂ may be from about 0.2 to about 0.6. The second patterning process may be repeated until the first openings 104 reach a depth D₂ from about 10 μm to about 100 μm, such as about 50 μm. A depth D₃ of the second region 104 b of the first openings may be from about 10 μm to about 90 μm, such as about 40 μm.

The second depositions may be performed at a pressure from about 5 mTorr to about 200 mTorr, such as about 40 mTorr, with a primary plasma power in a range from about 1000 W to about 3000 W, such as about 2500 W and a secondary plasma power in a range from about 50 W to about 1000 W, such as about 400 W. The second depositions may be performed for a time period which ramps from a first time period during the first iteration to a second time period during the last iteration of the second patterning process. The first time period may be from about 0.5 seconds to about 5 seconds, such as about 1.0 second and the second time period may be from about 0.5 seconds to about 5 seconds, such as about 2.0 seconds.

The second depositions may utilize a primary deposition gas and a secondary deposition gas, which each include fluorine-containing gases such as difluoromethane (CH₂F₂), octafluoropropane (C₃F₈), octafluorocyclobutane (C₄F₈), sulfur hexafluoride (SF₆), combinations thereof, or the like. In some embodiments, a carrier gas, such as argon (Ar), may be included in the primary deposition gas and/or the secondary deposition gas. In an embodiment, the primary deposition gas includes sulfur hexafluoride at a flowrate from about 0 sccm to about 100 sccm, such as about 1 sccm and octafluorocyclobutane which ramps from a first flowrate during the first iteration to a second flowrate during the last iteration of the second patterning process. The first flowrate may be from about 50 sccm to about 500 sccm, such as about 250 sccm and the second flowrate may be from about 50 sccm to about 500 sccm, such as about 240 sccm. The secondary deposition gas may include octafluorocyclobutane at a flowrate from about 10 sccm to about 500 sccm, such as about 85 sccm and sulfur hexafluoride at a flowrate from about 0 sccm to about 100 sccm, such as about 1 sccm.

The second etchings may be performed at a pressure from about 5 mTorr to about 200 mTorr, such as about 30 mTorr, with a primary plasma power in a range from about 1000 W to about 3000 W, such as about 2500 W and a secondary plasma power in a range from about 50 W to about 1000 W, such as about 400 W. The second etchings may be performed using a substrate bias from about 5 W to about 1000 W, such as about 80 W. The second etchings may be performed for a time period which ramps from a first time period during the first iteration to a second time period during the last iteration of the second patterning process. The first time period may be from about 0.5 seconds to about 5 seconds, such as about 0.8 second and the second time period may be from about 0.5 seconds to about 5 seconds, such as about 2.9 seconds.

The second etchings may utilize a primary etching gas and a secondary etching gas, which each include fluorine-containing gases such as difluoromethane (CH₂F₂), octafluoropropane (C₃F₈), octafluorocyclobutane (C₄F₈), sulfur hexafluoride (SF₆), combinations thereof, or the like. In some embodiments, a carrier gas, such as argon (Ar), may be included in the primary etching gas and/or the secondary etching gas. In an embodiment, the primary etching gas includes octafluorocyclobutane at a flowrate from about 0 sccm to about 100 sccm, such as about 1 sccm and sulfur hexafluoride which ramps from a first flowrate during the first iteration to a second flowrate during the last iteration of the second patterning process. The first flowrate may be from about 10 sccm to about 1000 sccm, such as about 400 sccm and the second flowrate may be from about 10 sccm to about 1000 sccm, such as about 356 sccm. The secondary etching gas may include octafluorocyclobutane at a flowrate from about 0 sccm to about 100 sccm, such as about 1 sccm.

The third etchings may be performed at a pressure from about 5 mTorr to about 200 mTorr, such as about 40 mTorr, with a primary plasma power in a range from about 1000 W to about 3000 W, such as about 2500 W and a secondary plasma power in a range from about 50 W to about 1000 W, such as about 500 W. The third etchings may be performed using a substrate bias from about 0 W to about 1000 W, such as about 5 W. The third etchings may be performed for a time period which ramps from a first time period during the first iteration to a second time period during the last iteration of the second patterning process. The first time period may be from about 0.5 seconds to about 5 seconds, such as about 0.8 second and the second time period may be from about 0.5 seconds to about 5 seconds, such as about 3.6 seconds.

The third etchings may utilize a primary etching gas and a secondary etching gas, which each include fluorine-containing gases such as difluoromethane (CH₂F₂), octafluoropropane (C₃F₈), octafluorocyclobutane (C₄F₈), sulfur hexafluoride (SF₆), combinations thereof, or the like. In some embodiments, a carrier gas, such as argon (Ar), may be included in the primary etching gas and/or the secondary etching gas. In an embodiment, the primary etching gas includes octafluorocyclobutane at a flowrate from about 0 sccm to about 100 sccm, such as about 1 sccm and sulfur hexafluoride which ramps from a first flowrate during the first iteration to a second flowrate during the last iteration of the second patterning process. The first flowrate may be from about 10 sccm to about 1000 sccm, such as about 400 sccm and the second flowrate may be from about 10 sccm to about 1000 sccm, such as about 356 sccm. The secondary etching gas may include octafluorocyclobutane at a flowrate from about 0 sccm to about 100 sccm, such as about 1 sccm.

FIGS. 3A and 3B illustrate a removal of the patterned photoresist 102 and a deposition of a first metal layer 110 over the first semiconductor substrate 100 and in the first openings 104, in accordance with some embodiments. FIG. 3B illustrates a detailed view of region 112 of FIG. 3A. After the first openings 104 are formed in the first semiconductor substrate 100, the patterned photoresist 102 may be removed using suitable photoresist stripping techniques, such as chemical solvent cleaning, plasma ashing, dry stripping and/or the like.

The first metal layer 110 may be deposited by sputter deposition, physical vapor deposition (PVD), chemical vapor deposition (CVD), or the like. The first metal layer 110 may include conductive materials such as metals. The first metal layer 110 may include metals such as copper, titanium, tungsten, aluminum, gold, combinations thereof, or the like. In a specific embodiment, the first metal layer 110 may comprise a titanium layer and a gold layer deposited over the titanium layer. The titanium layer may have a thickness form about 10 nm to about 500 nm, such as about 100 nm, and the gold layer may have a thickness form about 10 nm to about 1000 nm, such as about 400 nm. The first metal layer 110 may have a thickness from about 20 nm to about 1500 nm, such as about 500 nm.

In some embodiments, the first metal layer 110 may have a thickness greater than the depth S₁ of the first scallops 108 a and less than the depth S₂ of the second scallops 108 b. As illustrated in FIG. 3B, this results in the first metal layer 110 filling the first scallops 108 a, without filling the second scallops 108 b, such that the first metal layer 110 is continuous in the first region 104 a and discontinuous in the second region 104 b. This provides good conductivity in the first region 104 a of the first openings 104, and insulation in the second region 104 b of the first openings 104.

The devices included in the first semiconductor substrate 100 may be disposed in a portion of the first semiconductor substrate 100 up to the depth D1. The first metal layer 110 may be coupled to the first semiconductor substrate 100 and may be included to provide shielding for the devices included in the first semiconductor substrate 100. The first metal layer 110 provides a grounding electrical path to the first semiconductor substrate 100 and provides electrostatic discharge (ESD) protection in some embodiments.

In other embodiments, the first metal layer 110 may have a thickness greater than the depth S₁ of the first scallops 108 a and greater than the depth S₂ of the second scallops 108 b. For example, the first metal layer 110 may have a thickness from about 20 nm to about 1500 nm, such as about 500 nm. As a result, both the first scallops 108 a and the second scallops 108 b may be filled with the first metal layer 110 and the first metal layer 110 may be continuous along the top surface of the first semiconductor substrate 100, along sidewalls of the first openings 104, and along the bottom surface of the first openings 104. This provides conductivity in both the first region 104 a and the second region 104 b of the first openings 104, with the first region 104 a having better conductivity than the second region 104 b. By controlling the thickness of the first metal layer 110, and the depths of the first scallops 108 a and the second scallops 108 b, the conductivity in the first region 104 a and the second region 104 b of the first openings 104 may be controlled and shielding may be provided depending on customer's needs.

FIG. 4 illustrates a deposition of a sacrificial material 114 in the first openings 104 and a bonding of a carrier substrate 120 to the first semiconductor substrate 100, in accordance with some embodiments. The sacrificial material 114 may comprise silicon oxide, silicon oxynitride, SiCON, SiC, SiOC, and/or silicon nitride and may be deposited using CVD, atomic layer deposition (ALD), PVD, spin-on coating, the like, or a combination thereof. The sacrificial material 114 may be deposited such that the sacrificial material 114 fills the first openings 104 and extends over the first semiconductor substrate 100. The sacrificial material 114 may then be planarized such that top surfaces of the sacrificial material 114 are level with top surfaces of the first metal layer 110. A process such as chemical mechanical polishing (CMP) may be used to planarize the sacrificial material 114.

A first passivation film 116 is then formed over the first metal layer 110 and the sacrificial material 114. The first passivation film 116 may be formed by thermal oxidation, CVD, PVD, or the like. The first passivation film 116 may comprise any suitable dielectric material that can be directly bonded to another dielectric layer in a subsequent process step. For example, the first passivation film 116 may comprise silicon oxide (e.g., SiO₂), silicon oxynitride, silicon nitride, or the like.

The carrier substrate 120 may include a bulk semiconductor substrate, semiconductor-on-insulator (SOI) substrate, multi-layered semiconductor substrate, or the like. The semiconductor material of the carrier substrate 120 may be silicon, germanium, a compound semiconductor including silicon germanium, silicon carbide, gallium arsenic, gallium phosphide, indium phosphide, indium arsenide, and/or indium antimonide; an alloy semiconductor including SiGe, GaAsP, AlInAs, AlGaAs, GaInAs, GaInP, and/or GaInAsP; or combinations thereof. Other substrates, such as multi-layered or gradient substrates, may also be used. The carrier substrate 120 may be doped or undoped.

A second passivation film 118 is disposed on the carrier substrate 120. The second passivation film 118 may comprise any suitable dielectric material that can be directly bonded to another dielectric layer in a subsequent process step. For example, the second passivation film 118 may comprise silicon oxide (e.g., SiO₂), silicon oxynitride, silicon nitride, or the like.

The first passivation film 116 of the first semiconductor substrate 100 may be physically contacted and bonded to the second passivation film 118 of the carrier substrate 120. Prior to bonding, at least one of the first passivation film 116 or the second passivation film 118 may be subjected to a surface treatment. The surface treatment may be a plasma treatment. The plasma treatment may be performed in a vacuum environment. The process gas used for generating the plasma may be a hydrogen-containing gas, which includes a first gas including hydrogen (H₂) and argon (Ar), a second gas including H₂ and nitrogen (N₂), or a third gas including H₂ and helium (He). Through the surface treatment, the number of —OH groups at the surface of the first passivation film 116 and/or the second passivation film 118 increases, which is beneficial for forming strong fusion bonds. The plasma treatment may also be performed using pure or substantially pure H₂, Ar, or N₂ as the process gas, which treats the surfaces of the first passivation film 116 and/or the second passivation film 118 through reduction and/or bombardment. After the surface treatment, a cleaning process (e.g., a rinse with deionized water) may be applied to the first passivation film 116 and/or the second passivation film 118.

After the cleaning process, the first semiconductor substrate 100 and the carrier substrate 120 are pressed against each other. A pre-bonding pressing force may be applied to press the first semiconductor substrate 100 and the carrier substrate 120 against each other. A pressing force of less than about 5 N may be applied to each of the first semiconductor substrate 100 and the carrier substrate 120 in some exemplary embodiments, although a greater or a smaller force may also be used. The pre-bonding may be performed at room temperature (e.g., between about 21° C. and about 25° C.), although higher temperatures may be used. The bonding time may be shorter than about 1 minute, for example.

After the pre-bonding, the first passivation film 116 and the second passivation film 118 are bonded to each other. The bond, however, may be strengthened in a subsequent annealing step. For example, an optional annealing at a temperature of about 170° C. for about 1 hour may be performed on the first semiconductor substrate 100 and the carrier substrate 120. When the temperature rises, the —OH bonds in the first passivation film 116 and the second passivation film 118 break to form strong Si—O—Si bonds, and hence the first semiconductor substrate 100 and the carrier substrate 120 are bonded to each other through fusion bonds.

FIG. 5 illustrates a flipping of the structure illustrated in FIG. 4 and a thinning of the first semiconductor substrate 100, in accordance with some embodiments. After the first semiconductor substrate 100 and the carrier substrate 120 are bonded, a thinning process may be applied to the first semiconductor substrate 100. The thinning process may include grinding or CMP processes, etch back processes, or other acceptable processes performed on a surface of the first semiconductor substrate 100. The first semiconductor substrate 100 may be thinned to expose the sacrificial material 114. Following the thinning process, the first semiconductor substrate 100 may have a thickness T1 from about 10 μm to about 100 μm, such as about 50 μm.

FIG. 6 illustrates a bonding of a second semiconductor substrate 122 to the first semiconductor substrate 100, in accordance with some embodiments. A third passivation film 124 is formed over the first semiconductor substrate 100 and the sacrificial material 114. The third passivation film 124 may be formed by thermal oxidation, CVD, PVD, or the like. The third passivation film 124 may comprise any suitable dielectric material that can be directly bonded to another dielectric layer in a subsequent process step. For example, the third passivation film 124 may comprise silicon oxide (e.g., SiO₂), silicon oxynitride, silicon nitride, or the like.

The second semiconductor substrate 122 may include a bulk semiconductor substrate, semiconductor-on-insulator (SOI) substrate, multi-layered semiconductor substrate, or the like. The semiconductor material of the second semiconductor substrate 122 may be silicon, germanium, a compound semiconductor including silicon germanium, silicon carbide, gallium arsenic, gallium phosphide, indium phosphide, indium arsenide, and/or indium antimonide; an alloy semiconductor including SiGe, GaAsP, AlInAs, AlGaAs, GaInAs, GaInP, and/or GaInAsP; or combinations thereof. Other substrates, such as multi-layered or gradient substrates, may also be used. The second semiconductor substrate 122 may be doped or undoped.

A fourth passivation film 126 is disposed on the second semiconductor substrate 122. The fourth passivation film 126 may comprise any suitable dielectric material that can be directly bonded to another dielectric layer in a subsequent process step. For example, the fourth passivation film 126 may comprise silicon oxide (e.g., SiO₂), silicon oxynitride, silicon nitride, or the like.

The third passivation film 124 of the first semiconductor substrate 100 may be physically contacted and bonded to the fourth passivation film 126 of the second semiconductor substrate 122. The third passivation film 124 may be bonded to the fourth passivation film 126 using the same bonding process described above with respect to FIG. 4. For example, prior to bonding, at least one of the third passivation film 124 or the fourth passivation film 126 may be subjected to a surface treatment, which may be a plasma treatment. After the surface treatment, a cleaning process (e.g., a rinse with deionized water) may be applied to the third passivation film 124 and/or the fourth passivation film 126. After the cleaning process, the first semiconductor substrate 100 and the second semiconductor substrate 122 are pressed against each other to cause pre-bonding between the third passivation film 124 and the fourth passivation film 126. Finally, the bonds between the third passivation film 124 and the fourth passivation film 126 may be strengthened by a subsequent annealing step.

FIG. 7 illustrates a formation of cavity 128 and second openings 130, in accordance with some embodiments. The cavity 128 may be formed by etching the second semiconductor substrate 122. The second semiconductor substrate 122 may be etched using an anisotropic etch process, such as reactive ion etching (RIE), neutral beam etching (NBE), or the like. In some embodiments, the fourth passivation film 126 may act as an etch stop layer for etching the cavity 128 in the second semiconductor substrate 122. As illustrated in FIG. 7, the cavity 128 may extend completely through the second semiconductor substrate 122. As further illustrated in FIG. 7, the cavity 128 may taper from a first width W₁ distal the first semiconductor substrate 100 to a second width W₂ proximal the first semiconductor substrate 100. The cavity may have a depth D₄ from about 100 μm to about 800 μm, the first width W₁ may be from about 14 mm to about 18 mm, and the second width W2 may be from about 12 mm to about 16 mm.

After the cavity 128 is etched through the second semiconductor substrate 122, the fourth passivation film 126 and the third passivation film 124 may be etched to extend the cavity 128 to the first semiconductor substrate 100 and the sacrificial material 114, the second passivation film 118, and the first passivation film 116 may be etched to form the second openings 130. In some embodiments, the fourth passivation film 126, the third passivation film 124, the sacrificial material 114, the second passivation film 118, and the first passivation film 116 may be formed of the same materials. For example, the fourth passivation film 126, the third passivation film 124, the sacrificial material 114, the second passivation film 118, and the first passivation film 116 may be formed of silicon oxide. In further embodiments, different materials may be used for any of the fourth passivation film 126, the third passivation film 124, the sacrificial material 114, the second passivation film 118, and the first passivation film 116. The fourth passivation film 126, the third passivation film 124, the sacrificial material 114, the second passivation film 118, and the first passivation film 116 may be etched using dry etch processes or wet etch processes and may be etched in a single etch process or multiple etch processes. As illustrated in FIG. 7, following the etching of the second semiconductor substrate 122, the fourth passivation film 126, the third passivation film 124, the sacrificial material 114, the second passivation film 118, and the first passivation film 116, side surfaces of the second semiconductor substrate 122, the fourth passivation film 126, and the third passivation film 124 and top surfaces of the first semiconductor substrate 100 are exposed in the cavity 128. Further, side surfaces of the first semiconductor substrate 100, the first metal layer 110, the second passivation film 118, and the first passivation film 116 and top surfaces of the first metal layer 110 and the carrier substrate 120 are exposed in the second openings 130.

FIGS. 8A and 8B illustrate a formation of a second metal layer 132 over the second semiconductor substrate 122, in the cavity 128, and in the second openings 130, in accordance with some embodiments. FIG. 8B illustrates a detailed view of region 134 of FIG. 8A. The second metal layer 132 may be deposited by sputter deposition, PVD, CVD, or the like. The second metal layer 132 may include conductive materials such as metals. The second metal layer 132 may include metals such as copper, titanium, tungsten, aluminum, gold, combinations thereof, or the like. In a specific embodiment, second metal layer 132 may comprise a titanium layer and a gold layer deposited over the titanium layer. The titanium layer may have a thickness form about 10 nm to about 500 nm, such as about 100 nm, and the gold layer may have a thickness form about 10 nm to about 1000 nm, such as about 200 nm. The second metal layer 132 may have a thickness from about 20 nm to about 1500 nm, such as about 300 nm.

In some embodiments, the second metal layer 132 and the first metal layer 110 may have a combined thickness greater than the depth S₁ of the first scallops 108 a and less than the depth S₂ of the second scallops 108 b. As illustrated in FIG. 8B, this results in the second metal layer 132 and the first metal layer 110 filling the first scallops 108 a, without filling the second scallops 108 b, such that the second metal layer 132 and the first metal layer 110 are continuous in the first region 104 a and discontinuous in the second region 104 b. This provides good conductivity in the first region 104 a of the second openings 130, and insulation in the second region 104 b of the second openings 130.

The second metal layer 132 and the first metal layer 110 may be coupled to the first semiconductor substrate 100 and/or the second semiconductor substrate 122 and may be included to provide shielding for the devices included in the first semiconductor substrate 100 and/or the second semiconductor substrate 122. The second metal layer 132 and the first metal layer 110 provide grounding electrical paths to the first semiconductor substrate 100 and/or the second semiconductor substrate 122 and provide electrostatic discharge (ESD) protection in some embodiments.

In other embodiments, the second metal layer 132 and the first metal layer 110 may have a combined thickness greater than the depth S₁ of the first scallops 108 a and greater than the depth S₂ of the second scallops 108 b. For example, the second metal layer 132 and the first metal layer 110 may have a combined thickness from about 20 nm to about 1500 nm, such as about 300 nm. As a result, both the first scallops 108 a and the second scallops 108 b may be filled with the second metal layer 132 and the first metal layer 110 and the second metal layer 132 and the first metal layer 110 may be continuous along the top surface of the second semiconductor substrate 122, along surfaces of the cavity 128, along surfaces of the first semiconductor substrate forming sidewalls of the second openings 130, and along the bottom surface of the first semiconductor substrate 100 (e.g., in the orientation illustrated in FIGS. 8A and 8B). This provides conductivity in both the first region 104 a and the second region 104 b of the second openings 130, with the first region 104 a having better conductivity than the second region 104 b. By controlling the thicknesses of the second metal layer 132 and the first metal layer 110, and the depths of the first scallops 108 a and the second scallops 108 b, the conductivity in the first region 104 a and the second region 104 b of the second openings 130 may be controlled and shielding may be provided depending on customer's needs. Some embodiments may include the first metal layer 110 only, the second metal layer 132 only, or combinations of the first metal layer 110 and the second metal layer 132.

FIG. 9 illustrates a formation of a semiconductor device 150 following a removal of the carrier substrate 120, the first passivation film 116, and the second passivation film 118 and a planarization of portions of the second metal layer 132. Processes such as grinding or CMP processes, etch back processes, or other acceptable processes may be used to remove the carrier substrate 120, the first passivation film 116, and the second passivation film 118 and to planarize the second metal layer 132.

The semiconductor device 150 may further be singulated from other semiconductor devices by performing a singulation process along scribe lines 136 (illustrated in FIG. 8A). The singulation may be by sawing, laser drilling, or the like along the scribe lines 136. The singulation process separates the semiconductor device 150 from adjacent semiconductor devices.

The first metal layer 110 and/or the second metal layer 132 may be used to provide shielding in the semiconductor device 150. Using the first patterning process and the second patterning process forms the first scallops 108 a and the second scallops 108 b, respectively, in the first openings 104 with different depths in the first region 104 a and the second region 104 b. This provides control of the conductivity of first metal layer 110 and/or the second metal layer 132 in the first region 104 a and the second region 104 b, without requiring additional deposition and etching steps, and reduces the cost of forming the semiconductor device 150.

In accordance with an embodiment, a semiconductor device includes a first substrate; and a through via extending through the first substrate, the first substrate including a first plurality of scallops adjacent the through via in a first region of the first substrate, each of the scallops of the first plurality of scallops having a first depth; and a second plurality of scallops adjacent the through via in a second region of the first substrate, each of the scallops of the second plurality of scallops having a second depth, the second depth being greater than the first depth. In an embodiment, the first depth is from 30 nm to 50 nm and the second depth is from 150 nm to 250 nm. In an embodiment, a ratio of the first depth to the second depth is from 0.2 to 0.6. In an embodiment, the through via includes a metal layer adjacent the first substrate, the metal layer having a thickness greater than the first depth and less than the second depth. In an embodiment, the metal layer is continuous in the first region and discontinuous in the second region. In an embodiment, the first substrate includes a first surface and a second surface opposite the first surface, the first region extending from the first surface to a point between the first surface and the second surface, and the second region extending from the point to the second surface. In an embodiment, the semiconductor device further includes a second substrate bonded to the first substrate, a cavity extending through the second substrate, the cavity having tapered sidewalls. In an embodiment, the semiconductor device further includes a first passivation film and a second passivation film interposed between the first substrate and the second substrate, the second substrate being bonded to the first substrate by dielectric-to-dielectric bonds between the first passivation film and the second passivation film.

In accordance with another embodiment, a method includes etching a substrate with a first patterning process to form an opening in the substrate extending from a first surface of the substrate to a first depth, the first patterning process including a plurality of first iterations, each of the first iterations including a first deposition and a first etch; and etching the substrate with a second patterning process to extend the opening in the substrate from the first depth to a second depth, the second patterning process including a plurality of second iterations, each of the second iterations including a second deposition, a second etch, and a third etch, the third etch having different process parameters from the first etch and the second etch. In an embodiment, the first patterning process includes from 50 to 150 first iterations and the second patterning process includes from 50 to 500 second iterations. In an embodiment, the etching the substrate with the first patterning process forms first scallops in sidewalls of the opening having a depth from about 40 nm to about 90 nm. In an embodiment, the etching the substrate with the second patterning process forms second scallops in sidewalls of the opening having a depth from about 100 nm to about 300 nm. In an embodiment, the first depth is from 4 μm to 17 μm and the second depth is from 10 μm to 100 μm. In an embodiment, a process gas for the first deposition and the second deposition includes octafluorocyclobutane (C₄F₈) and a process gas for the first etch, the second etch, and the third etch includes sulfur hexafluoride (SF₆).

In accordance with yet another embodiment, a method includes etching a substrate to form a first opening including a first region and a second region, the first region extending from a surface of the substrate to a first depth in the substrate, the second region extending from the first depth to a second depth in the substrate, the etching including performing a first patterning process to form the first opening in the first region, the first patterning process including a plurality of first patterning iterations; and performing a second patterning process to form the first opening in the second region, the second patterning process including a plurality of second patterning iterations, wherein a duration of each of the second patterning iterations is greater than a duration of each of the first patterning iterations; and depositing a metal layer along sidewalls of the first opening, a conductivity of the metal layer in the first region being less than a conductivity of the metal layer in the second region. In an embodiment, sidewalls of the first opening in the first region include scallops having a first depth, sidewalls of the first opening in the second region include scallops having a second depth, and the metal layer is deposited to a thickness between the first depth and the second depth. In an embodiment, the second depth is greater than the first depth, and the metal layer is deposited such that the metal layer is continuous in the first region and discontinuous in the second region. In an embodiment, the metal layer is deposited by sputter deposition. In an embodiment, sidewalls of the first opening in the first region include scallops having a first depth, sidewalls of the first opening in the second region include scallops having a second depth, and the metal layer is deposited to a thickness greater than the each of the first depth and the second depth. In an embodiment, the second depth is greater than the first depth, and the metal layer is continuous in both the first region and the second region.

The foregoing outlines features of several embodiments so that those skilled in the art may better understand the aspects of the present disclosure. Those skilled in the art should appreciate that they may readily use the present disclosure as a basis for designing or modifying other processes and structures for carrying out the same purposes and/or achieving the same advantages of the embodiments introduced herein. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the present disclosure, and that they may make various changes, substitutions, and alterations herein without departing from the spirit and scope of the present disclosure. 

What is claimed is:
 1. A semiconductor device comprising: a first substrate; a through via extending through the first substrate, the first substrate comprising: a first plurality of scallops adjacent the through via in a first region of the first substrate, each of the scallops of the first plurality of scallops having a first depth; and a second plurality of scallops adjacent the through via in a second region of the first substrate, each of the scallops of the second plurality of scallops having a second depth, wherein the second depth is greater than the first depth; and a first metal layer on the first substrate, the first metal layer having a thickness greater than the first depth and less than the second depth.
 2. The semiconductor device of claim 1, wherein the first depth is from 30 nm to 50 nm and the second depth is from 150 nm to 250 nm.
 3. The semiconductor device of claim 1, wherein a ratio of the first depth to the second depth is from 0.2 to 0.6.
 4. The semiconductor device of claim 1, wherein the first metal layer is continuous in the first region and discontinuous in the second region.
 5. The semiconductor device of claim 1, wherein the first substrate comprises a first surface and a second surface opposite the first surface, wherein the first region extends from the first surface to a point between the first surface and the second surface, and wherein the second region extends from the point to the second surface.
 6. The semiconductor device of claim 1, further comprising a second substrate bonded to the first substrate, wherein a cavity extends through the second substrate, wherein the cavity has tapered sidewalls.
 7. The semiconductor device of claim 6, further comprising a first passivation film and a second passivation film interposed between the first substrate and the second substrate, wherein the second substrate is bonded to the first substrate by dielectric-to-dielectric bonds between the first passivation film and the second passivation film.
 8. The semiconductor device of claim 1, further comprising a second metal layer on the first substrate and the first metal layer, wherein the first metal layer and the second metal layer have a combined thickness less than the second depth.
 9. A semiconductor device comprising: a first substrate comprising a first opening extending through the first substrate, wherein the first opening comprises a first region extending from a first surface of the first substrate to a first depth, wherein the first opening further comprises a second region extending from the first depth to a second surface of the first substrate opposite the first surface; and a first metal layer extending along sidewalls of the first opening, wherein the first metal layer is continuous in the first region of the first opening, and wherein the first metal layer is discontinuous in the second region of the first opening.
 10. The semiconductor device of claim 9, wherein the first region comprises a plurality of first scallops adjacent the first opening, wherein the second region comprises a plurality of second scallops adjacent the first opening, and wherein a second depth of the first scallops is less than a third depth of the second scallops.
 11. The semiconductor device of claim 10, wherein the first metal layer has a thickness greater than the second depth and less than the third depth.
 12. The semiconductor device of claim 10, wherein the second depth is in a range from 40 nm to 90 nm, and wherein the third depth is in a range from 100 nm to 300 nm.
 13. The semiconductor device of claim 10, wherein the second depth is in a range from 4 μm to 17 μm, and wherein the third depth is in a range from 10 μm to 100 μm.
 14. The semiconductor device of claim 9, wherein the first region comprises a plurality of first scallops adjacent the first opening, wherein the second region comprises a plurality of second scallops adjacent the first opening, wherein the plurality of first scallops comprises 50 to 150 of the first scallops, and wherein the plurality of second scallops comprises 50 to 500 of the second scallops.
 15. A device comprising: a substrate comprising a first opening, the first opening comprising a first region and a second region, wherein the first region extends from a surface of the substrate to a first depth in the substrate, wherein the second region extends from the first depth through the substrate, wherein the substrate comprises: a plurality of first scallops adjacent the first region of the first opening, the first scallops extending to a second depth; and a plurality of second scallops adjacent the second region of the first opening, the second scallops extending to a third depth greater than the second depth; and a metal layer extending along side surfaces of the substrate in the first opening, wherein a conductivity of the metal layer in the first region of the first opening is greater than a conductivity of the metal layer in the second region of the first opening.
 16. The device of claim 15, wherein the metal layer has a thickness between the second depth and the third depth.
 17. The device of claim 16, wherein the metal layer is continuous in the first region and discontinuous in the second region.
 18. The device of claim 15, wherein the metal layer has a thickness greater than the second depth and the third depth.
 19. The device of claim 18, wherein the metal layer is continuous in the first region and the second region.
 20. The device of claim 15, wherein a ratio of the second depth to the third depth is from 0.2 to 0.6. 